Ang Lee's follow-up to Brokeback Mountain is Lust, Caution. The film's receipt of an NC-17 by the MPAA was dutifully noted by the mainstream media, as was the distributor's (Focus Features) decision not to appeal the rating. NC-17 movies arenít released often and, when they are, they rarely make an impression at the box office - some mainstream multiplex chains refuse to show them and some newspapers will not advertise them. This has earned the NC-17 the nickname of the "kiss of death." So, before discussing the merits of Lust, Caution, I'll first answer a question at least a few readers are interested in understanding: Why the NC-17? What is there about this movie that makes it cross the border from the ever-widening realm of the R?

The answer: the sex is really hot. Not hardcore pornographic (at least by my definition of the term) but close. Of course, for those thinking this might be a fun way to mix art and sex, keep in mind that the movie is about 160 minutes long. Of the 160 minutes, maybe 10 feature sex and/or nudity. Not a good ratio if that's all you're after. The sex scenes are so intense and explicit (showing pretty much everything except an erect penis and penetration) that someone asked Lee in a recent press conference if the acts are real or simulated. His response: "Have you seen the film?" Lead actor Tony Leung has been equally cryptic in interviews. The goal appears to be to create an aura of mystery about the sex scenes. One is tempted to say that passion this raw can't be faked, but we're dealing with good actors. So it remains an open question whether Lust, Caution follows in the footsteps of Boxcar Bertha and Wild Orchid. (Two mainstream films in which the participants later admitted to having not simulated the sex.) The bottom line, however, is that the characters reveal more about themselves during the sex scenes than at any other time in the film. When they're naked and thrusting and contorting their bodies and faces, that's when we see their real interaction. As a result, it's impossible to argue that the sex scenes are gratuitous. Without them, a lot of the film's emotional underpinning goes away.

Lust, Caution features a slow seduction of one character by another and the audience by the director. The buildup is long and lingering - some might argue too long. There are times during the first two hours when the pacing lags. To a large degree, that's compensated for by a wrenching final act when morality is upturned and consequences abound. In every way, this is an atypical thriller. Itís beautiful to look at (the period detail is superb) and sexy as hell, but it sometimes feels like it's never going to get to the finish line. Nevertheless, I stayed awake and engrossed through the whole thing and couldn't get it out of my head after exiting. Its haunting fascination is hard to deny.

Curiously, the movie shares some general plot similarities with Paul Verhoeven's Black Book. Both are World War II stories that transpire in occupied territories. Both feature female protagonists working for the local resistance. And both women have affairs with highly placed enemy officials, then become conflicted as a result of unexpected feelings they develop for those men. There are two significant differences, however, and those aspects result in the pictures offering divergent experiences. The first relates to location. Black Book unfolds in Nazi territory while Lust, Caution splits time between Shanghai and Hong Kong. More importantly, the way in which the stories are told are in sharp contrast. Verhoevenís in-your-face action approach is 180 degrees away from Leeís languorous style.

The film takes us to the years between 1938 and 1942. Wang (Tang Wei in a stunning, courageous debut performance) is a traditional Chinese "good girl" who has become a war orphan (her mother is dead, her father is "trapped" in England). As a result of a crush on a dashing young activist (Wang Lee-Hom), she joins a patriotic theater troupe. The group eventually graduates from putting on politically subversive pageants to taking a more active role in resistance activities, including assassinations. Wang is set up to become the mistress of the highly placed collaborator Mr. Yee (a flawless Tony Leung Chiu Wai) as part of a plot to kill him, but before the relationship can be consummated, Yee is recalled from Hong Kong to Shanghai. It's three years before Wang can follow him and resume her charade. This time, things are in earnest. Yee is now the head of the secret service and is a ripe target for elimination. But when Wang becomes his lover, complications in the form of unwanted emotional entanglements threaten the operation.

Another notable element in Lust, Caution is the amount of nonverbal communication that occurs. This is especially evident during the mahjong game that opens the film. The four women around the table hold a banal conversation while their glances and gestures hint that there's another level of interaction transpiring beneath the surface - especially when Mr. Yee enters the room. There are numerous scenes in which more information is conveyed by reading how the characters act and move than by listening to what they say. It has been rightly said that it can be easier to lie with words than with glances.

Lust, Caution is one of those films that requires patience. Like cold water brought to a boil, it takes a long time but once the bubbles start appearing, the roiling is impossible to stop. Lee, who has never been one to stand pat or rest in a particular genre (this is, after all, a filmmaker who has been responsible for such diverse fare as Crouching Tiger, Hulk, and Brokeback Mountain) moves fluidly into new territory and conquers it with an ease that is almost breathless. Aided by the nuanced, forceful performances of his two leads, he has made Lust, Caution something to be seen and savored.